disinfection.ppt
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The document provides a historical review of chemical disinfection, detailing various disinfectants used throughout history, their definitions, modes of action, and properties of ideal disinfectants. It also classifies disinfectants based on their level of action and highlights practical applications in areas such as water treatment, wound disinfection, and sterilization of medical equipment. Additionally, it emphasizes the importance of hospital policies for effective disinfection and sterilization procedures.
disinfection.ppt
- 2. Historical Review • Wine used externally & internally • 1363 - Brandy used for military dressing • 1830 - Tincture of iodine US pharmacopoeia • 1832 - Creosote (phenol) “I preserve flesh “in Greek • 1854 - Hypochlorites used in hospital wards • 1905 – Kinnaman, disinfectant action of chemicals
- 3. Definitions • Sterilization • Disinfection • Antisepsis • Decontamination
- 4. Definitions • Sterilisation – Process by which an article, surface or medium is freed of all living microorganisms either in the vegetetative or spore state. • Disinfection – Destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection.
- 5. Definitions • Antisepsis – Prevention of infection, usually by inhibiting the growth of bacteria in wounds or tissues. •Decontamination – Process of rendering an article or area free of contaminants eg.microbial, chemical etc.
- 6. Properties ; Ideal Disinfectant • Wide spectrum of activity • Active in presence of organic matter • Effective in acid & alkaline media • Speedy action • High penetrating power
- 7. Properties ; Ideal Disinfectant • Stable • Compatible with other antiseptics & disinfectants • Non corrosive, non irritant & non toxic • Cheap & easily available • Safe & easy to use
- 8. Modes of action • Protein coagulation • Disruption of cell membrane • Removal of sulphydryl groups essential for enzyme functioning • Substrate competition
- 9. Levels of Disinfectant Action BACTERIA FUNGI VIRUSES Disinfectant Level Spores Tubercle Bacillus Vegeta tive Cells Fungi Non lipid and Small Lipid and Medium Sized High +‡ + + + + + Intermediate S + + + ±(in high conc|) + Low - - + ± ± +
- 10. Classification Low & Intermediate level • Halogens • Alcohols • Phenols • Dyes • Metallic salts • Surface active agents High level • Aldehydes • Peroxygen Compounds
- 11. PRIONS BACTERIAL SPORES MYCOBACTERIA PARASITIC CYSTS SMALL NON ENVELOPED VIRUSES TROPHOZOITES NON SPORULATING GRAM NEGATIVE BACTERIA FUNGI LARGE NON ENVELOPED VIRUSES NON SPORULATING GRAM POSITIVE BACTERIA ENVELOPED VIRUSES HIGHEST LOWEST
- 12. Halogens • Chlorine & chlorine compounds – Chlorine – Hypochlorites – Chlorine dioxide – Chloramines • Iodine & iodine compounds – Iodine & iodide – Iodophors – Preparations producing iodine in situ
- 13. Chlorine & Chlorine Compounds • Mechanism of action Cl + H2O → HOCl + H++ Cl- Oxidize thiol gps and halogenate –NH2 gps in proteins • Advantages – Low cost – Rapidity of action – Broad antimicrobial activity • Disadvantages – Corrosiveness – Inactivation by organic matter – Chemical instability.
- 14. Practical applications • Water treatment – Drinking water – Swimming pools – Sewage & waste water • Disinfection of open wounds & dental therapy – Hypochlorites & organic chloramines • Disinfection of equipment, instruments & laundry • Decontamination – Blood and body fluid spills – Bedpans, urinals, and kidney bowls – Culture spills in the microbiology laboratory
- 15. Iodine & Iodine Compounds • Mode of action – Oxidation of -SH group – Iodination of phenolic & imidazolic groups of amino acids • Iodophores – Complex of iodine with a carrier • Carriers – neutral polymers e.g. polyvinylpyrrolidinone (Povidone Iodine) • ↑ solubility of iodine • Sustained release reservoir
- 16. Iodine & Iodine Compounds • Topical antiseptics • Topical Iodine soln (aq soln of 2% Iodine & 2.4% NaI ) • Tincture of iodine (2% Iodine & 2.4% NaI in aq ethanol) • Lugol’s iodine (5% Iodine with 10% KI) • Povidone iodine Preoperative preparation of skin Treatment of infected & burnt skin • Veterinary medicine • Disinfection of cow’s udder • Disinfection of water & air
- 17. Alcohols • Ethyl alcohol & isopropyl alcohol (70%) • Mode of action – Protein coagulation/denaturation • Range – Vegetative bacteria – Viruses (enveloped) – Fungus - Methyl alcohol – Protozoans • Disinfection of thermometers & stethoscopes • Skin antiseptics
- 18. Phenolic compounds • Coal tar – clear soln phenolics – black fluids • Fractionation of coal tar • Synthetic - phenol, cresol & xylenol • Bisphenols - two phenolic gps e.g. dichlorophane • Chlorhexidine
- 19. Phenolic compounds • Mode of action – At high conc - penetrates and destroys cell wall & precipitates cellular protein – In lower conc - inactivates essential enzymes • Disinfection of environmental surfaces and noncritical devices • Chlohexidine – Skin disinfection – Surgical hand disinfection – Obstetrics & gynaecology
- 20. Surface active agents • Amphophilic compounds • Hydrophilic gp • Lipophilic gp • On the basis of charge on polar group – Cationic (QAC) – Anionic • K laurate, Na lauryl sulphate (soaps, shampoos) – Nonionic • Stabilizers, wetting agents, detergents & emulsifiers – Amphoteric/ zwitter ions • Catonic & anionic charge • Nonionic at isoelectric pH
- 21. Surface active agents (Cationic) • Mode of action – Act on the PO4 gp of cell membrane → enter cell → denature proteins • Antimicrobial activity – Gram +ve & Gram –ve at higher conc – Spores, mycobacteria & viruses – no effect • Cetavlon(savlon), benzalkonium chloride & cetrimide • Disinfection of skin, bladder irrigation, diaper rash • Disadv : Gm -ve bacteria Pseudomonas and Proteus spp. capable of growing in these solutions
- 22. Peroxygen Compounds • Hydrogen peroxide • Peracetic acid • Performic acid • Perpropionic acid
- 23. Peroxygen Compounds • Mode of action – Cl- + H2O2 MPO OCl- + H2O – O2 - + H2O2 → OH + OH- + O2 – H2O2 + Fe 2+ → OH + OH- + Fe 3+ • Range of action – Bacteria, yeasts , fungi, viruses & spores • Applications – Antiseptic – Odor control in sewage treatment – Contact lens disinfectant
- 24. Gaseous Chemical Sterilization • Alkylating agents – Ethylene oxide (ETO) – Formaldehyde • Oxidizing agents – Ozone – Betapropiolactone (BPL) – Propylene oxide – Chlorine dioxide
- 25. Ethylene oxide (ETO) • Mode of action – Alkylating –NH2, -OH & -SH gps • Applications – Heart lung machine – Respirators – Dental equipment – Glass, metal, paper surfaces • Disadvantage – Explosive nature – Carcinogenic – Mutagenic
- 27. Glutaraldehyde • Saturated dialdehyde • Mode of action – Alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups • Contact time - 20 to 90 min • Chemosterilant - long contact time (6 to 10 hrs)
- 28. Glutaraldehyde • Advantages – Broad spectrum – Activity in presence of organic matter – Non corrosive action on metals, rubber& lenses • Disinfection of endoscopes, cystoscopes & anesthesia equipment (Cidex 2% soln)) • Dental surgical instruments
- 29. Formaldehyde • Less potent germicide • Fumigation of wards/ laboratories/ OTs (150g KMnO4 + 280 ml formalin/1000cu ft) • Application – Disinfection of dialysis systems and hemodialysis filters – 10% soln used as preservative
- 30. Metals Copper Silver Mercury Sulphate Acetate Citrate Nitrate Sulphadiazine Thiomersa Mercurochrome Phenyl mercuric nitrate •Fungicide •Algicide •Antisepsis •Disinfectant •Fungicide •Preservative
- 31. Dyes Aniline • Brilliant green • Malachite green • Crystal violet • Affected by presence of organic matter • Selective agents in culture media Acridine • Proflavine • Acriflavine • Euflavine • Not affected by presence of organic matter • Antisepsis • Gram +ve > gram –ve organisms • Bacteriostatic
- 32. Risk Stratification Of Hospital Environment High risk (Surgical instruments, endoscopes & catheters) Contact with broken skin or mucous membranes/introduced into body Intermediate risk (Resp & anesthetic equipment, thermometers) Intact skin/mucous membrane/body fluids Low risk (stethoscopes, beddings) Intact skin Minimal risk (floors, walls, ceilings) Not in close contact
- 33. Hospital Decontamination AIR Atomized propylene glycol, formaldehyde BATHS, WASH BOWLS & TOILETS Chlorine releasing compounds Regular cleaning(acids) BEDPANS & URINALS Decontamination RESPIRATORY & ANAESTHETIC EQUIPMENT Ethylene oxide Glutaraldehyde ENDOSCOPES Glutaraldehyde
- 34. Chemical Disinfection Of Surfaces • Doorknobs, sinks & bed rails • Intensive care units, surgical suites, and nurseries • Chlorine compounds (500ppm), phenol, or QACs • Walls and windows • Phenols, QACs, and chlorine compounds with 100 to 200 ppm Densely contaminated surfaces Sparsely contaminated surfaces
- 35. BACTERIAL SPORES Glutaraldehyde, formaldehyde vapour, Chlorine dioxide& peracetic acid BLOOD BORNE VIRUSES, HEPATITIS A & PRIONS Glutaraldehyde, 70% Alcohol, hypochlorites & iodophores MYCOBACTERIA Ethylene oxide, glutaraldehyde, chlorine dioxide Problem Microorganisms
- 36. Testing of Disinfectants • In vitro tests – Suspension tests • Qualitative - Rideal – Walker - Modified Chick Martin • Quantitative – Capacity tests • Kelsey Sykes test – Carrier tests • In use tests
- 37. Bacterial suspension Disinfectant solution Phenol Subculture a loopful after contact time Rideal – Walker Test Phenol coefficient Dilution of test disinfectant that sterilizes suspension in given time Dilution of phenol
- 38. Testing of Disinfectants • Modified Chick Martin – Organic matter – dried yeast or faeces • Capacity tests – The ability to retain activity in the presence of an increasing load • Carrier tests – Carrier ( 1 cm2 cotton cloth dipped in bacterial suspension) transferred to disinfectant & after fixed reaction time , subcultured
- 39. In Use Tests • Microbiological monitoring of environment • Sample taken & diluted plated • Growth of non sporulating bacteria Inadequate disinfectant
- 40. Resistance to Disinfectants • Intrinsic – Impaired uptake of the germicide – Production of biofilms • Extrinsic – Plasmids or transposons – inactivate germicide – Efflux pumps
- 41. Hospital Policy • Every hospital should implement a formal written policy for its disinfection and sterilization procedures • Which disinfectant should be used for a particular purpose • Safety aspects – Methods for preparing an accurate use dilution – Correct exposure time for each disinfectant – The contact times and concentrations recommended by the manufacturer must be strictly followed – Frequency of use
- 42. References • Seymour S Block; Disinfection Sterilization & Preservation; Vth edn • Russel Hugo & Ayliffe; Principles & practice of Disinfection Preservation & Sterilization; 3rd edn • R Ananthnarayan; Textbook Of Microbiology; VIth edn